Method of removing foreign matter from metal articles



Patented Sept. 2, 1941 METHOD OF REMOVING FOREIGN MATTE FROM METALARTICLES Gilbert 11. Orozco, East Cleveland, Ohio, assignor to GilronProducts 00., Cleveland, Ohio, a corporation of Ohio 7 No Drawing,Application September 3, 1938, Serial No. 228,451

2 Claims.

This invention relates to a method of removing foreign matter from metalarticles and particularly to a method of removing from metal articlessuperficial films of carbon, dust, and films such as stearates of lead,zinc, magnesium and lime, and other oil and grease films with whichmetal articles become coated during forming, drawing, bufling and othermanufacturing operations.

One of the principal objects of the present invention is to provide asimple and inexpensive method for removing such foreign matter quicklyand efiiciently without scrubbing.

A more specific object is to provide a method whereby both the films andsuperficial carbon can be removed at the same time from the articleswithout scrubbing.

Other objects and advantages will become apparent from the followingspecification:

In the manufacture of metal articles from steel 'or other metal stock inthe form of wire, rod, or

other blanks, the stock usually is formed into the desired shape bydrawing, stamping, folding and like operations and .in all of theseoperations, the stock must be lubricated. Many articles, though formedby other operations and without lubrication, are often subjected tobuffing operations preparatory to plating, enameling and the like.

The lubricants and compounds used in drawing, forming, buffing,burnishing and polishing carbon is freed from the metal or dies or bothand becomes mixed with the lubricant and thereby is .held on the articlein the form of superficial carbon films or granules.

other foreign matter.

In the case of ordinary plating of metal arti'cles, the article issubjected toa buffing or burnishing operation after plating. Theseoperations cause the plating material to flow and consequently anysuperficial" carbon, pigment,

and dust films which otherwise would cause discoloration of the finishedplated surface are the appearance of the finished surface.

The same is true of pigments in the compounds, dust, and

article is not subjected to any bumng or burnishing operation afterplating. Consequently,- if any superficial carbon, pigment, 'dust andlike films remain on the article when it is introduced 5 into theplating bath, such films show through the plated surface, giving it avery undesirable blotched appearance.

In cyanide plating, a cyanide plating bath, such as copper cyanide, zinccyanide and'the like is used. In this type of plating the removalof thecarbon, pigment, dust and like films is not so' necessary in manyinstances because if the article is subjected to the cyanide platingbath for a sufficient period, the cyanide bath will deoxydize or removesuch superficial foreign matter. However, it often is desirable that thefinished article have a very accurate finished dimension and that theplating coat be in excess of' a predetermined minimum thickness forpurposes of durability, and allowance must be made for the thickness ofthe plating material. The. thickness of the plating coat can becontrolled. accurately only .by controlling the time of exposure of thearticle to the bath. If superficial foreign matter is present on thearticle or any appreciable amount of grease, wax, or oil is present onthe article, part of the time of exposure of the article in-the cyanide.bath is lost due to the fact that the bath first removes .30 the filmsand .foreign matter and only 'when they are removed does the platingactually begin. Consequently, even in the case of cyanide plating, 'whenaccurate dimensions are required in the finished article or whenapredetermined minimum thickness of plating coat is requiredfordurability, it is necessary to remove the films and othersuperficial. foreign matter so that the thickness of the-coating can be.accurately determined from; the length of time of the exposure 40 of thearticle inthe bath. I

Therefore, it'is' necessary in all-types of plat- 4 ing that the'filmsof grease, oil, wax, and like foreign matter be removed, and in mosttypes I of plating, it is necessary, orat least. desirable,

thatthe foreign matter such as the superficial carbon, dust, pigment andother films also be removed. In all instances it is desirable, that. I

this removal be effected preparatory to the introduction of the articleinto the plating bath. Generally, the lubricants and compounds-mentioned include stearates, such as stearates of lead, zinc,magnesium, lime and other metals. Such stearates have a high meltingpoint and consequently become firmly attached to the In the case of.bright" plating, however, the metal stock during the drawing, forming,buliing and burnishing .operations so that when the oil or bath. Forvery small articles, a two-minarticle is formed and ready for platingand enameling, its surface is usually coated with a very tenacious filmof the stearate or other greases and waxes present. Likewise thesuperficial carbon, pigments, dust and other films, above mentioned,adhere to the lubricant films but even if fthelatter are removed, thecarbon and other foreign matter mechanically cling to the article andmust, be removed in some manner.

At present there is coming into use a steel known' as leaded steelwhich, in its composi 'tion, includes lead as a lubricant forsubsequentenameling of the articles do not remove the other foreign matter, suchas the superficial films of carbon, pigment, dust, and the like.

All such foreign matter can be removed by the present method whichcomprises heating the article for a predetermined interval or period oftime by subjecting it to a heated bath or spray of liquid, such as oilsand oil derivatives, waxes and other materials, which are liquid at thetemperature. required, and then withdrawing the article from the heatingliquid bath or spray and subjecting it, in heated condition, to a bathor spray of liquid detergent cleaner, such as an aqueous alkali cleaningsolution, which is at a temperature below that of the heating liquid,and preferably just below the boiling point of the liquid cleaner. Thetemperatures of the baths preferably are such that the added heat of thearticle causes violent, localized boiling action of the liquid cleanerat the surfaceof the article. No other operations are necessary toremove the stearate films and superficial carbon completely. I

Preferably, the temperature of the heating spray or bath always ishigher than the temperature of .the liquid cleaner as this results inquicker and more effective cleaning action and even removes thesuperficial carbon, dust, pigment, and the like as well as foreignmatter, such as the oil, grease and wax films.

Verydesirable results are obtained by ing the article to'oil as aheating liquid, the oil preferably being at about 250 F., though the oilmay be heated. to just-below its flashing point, if desired, and thenquenching the article, while it is in heated condition in a" heatedliquid cleaner such as an aqueous alkali cleaner which is between 212and 220 F., that is, about the boiling point of the particular cleaningsolution and su ject sufficient to prevent congealing of-the oil ,or

heating liquid which is on the article from the ing and cleaning liquid,themorerapid the to the heating bath is dependentfupon thethickness andvolume of the metal, thethicker-remin-ing greater time of expocure'topreceding operation. The higher thetempera ture of the heating liquidrelative to-the quench-.

ute period of exposure to the heating bath is entirely adequate.

Generally it is desirable to subject the article to the heating bath fora sufilcient period to bring the temperature of the articlesubstantially up to the temperature of the heating bath or to atemperature such that, even after the loss of heat during transfer ofthe article from the heating bath to the liquid cleaner, the article issumciently heated to cause the violent, localized, boiling of thedetergent cleaner at the surface of the article. The localized boilingaction ofthe cleaner is much-more rapid and violent than can be obtainedby heating the cleaner by extraneous means in any manner suitable forcommercial production. Furthermore, the transfer of heat from thearticle to the cleaner, instead of from the cleaner to the article,appears to accelerate the, cleaning action by effecting a mechanicalremoval of any superficial foreign matter.

Exactly how the removal of the films, superj a high boiling andvolatilization point. Mineral,

vegetable or animal oils or derivatives and mixtures thereof arepreferred as a heating liquid and appear to have a very beneficialeffect on the surface of the article. Mineral oil is very desirablebecause it is less expensive than other available liquids having thenecessary characteristics. Compartive tests of animal oils, fish oils,cotton seed oil and ordinary parafiine lubricating oils indicate thatthe ordinary parafline oil is as satisfactory as the other oils. Theheating liquid may be a material which is not technically a liquidbutwhich liquefies at the temperature required herein.

I If desired, some volatile, high vaporizing solvents for grease, suchas are well known and available on the market may be included with theoil but are not necessary and it does not appear that the additionalcost is warranted.

For the aqueous cleaning bath any of the well tic soda or soda ash,trisodium phosphate or combinations thereof, with emulsifying agents,are quite satisfactory.

The maintenance of the temperature of the oil greater than that of theaqueous alkali cleaning solution, while assisting in the eventualremoval of the grease films, is more important in effecting matter. a

After the cleaning operation herein described, 1! the article is to beplated, it may, before .plating, be subjected to the, usual 'wellknownprac-L tice of rinsing with cold-or lukewarm 75, then, if desired,pickling or cleaning electrolytiknown alkali commercial cleaners may beused. For example, cleaners which are primarily causcally in an alkalibath, and finally rinsing -with water.

I claim: 1. The method of removing foreign matter such as greasysubstances, superficial carbon,

'wax and soaps, from metal articles, comprising heating the article to atemperature materially above the boiling point of water by subjection ofthe article to hot oil, and then, before the article has lost anappreciable'portion of h the heat so imparted, immersing the article inan aqueous alkaline cleaning solution having a boiling point materiallybelow the temperature of the article when immersed and which solution isheated to nearly the boiling point thereof and which is wax and soapsfrom a metal article comprising heating the articlefor a predeterminedperiod by immersion in a bath of oil for a sumcient time to raise thesurface of the article to a temv perature materially above the boilingpoint of water, and immediately thereafter quenching the article bydipping the article in an aqueous alkaline detergent bath heated toabout the boiling point of said bath.

' GILBERT H. OROZCO.

